There are many types of add-on eyeglasses for double-layer eyeglasses. Some of them are attached to the bottom lenses through magnets, others are affixed to the bottom lenses with hooks. The traditional eyeglasses and the added-on glasses are sold in sets which means that one set of add-on glasses fits only a certain type of eyeglasses. That kind of arrangement is complicated and inconvenient to use or to carry.
There have been previous attempts to make a clip-on eyeglass frame for clipping to a bottom lenses bridge. Inventor Yiling Xie proposed a flexible spring to make resilient arms as described in Detachable shelter frame for mounting in front of a primary spectacle frame, as described in U.S. Pat. No. 6,464,352 issued Oct. 15, 2002, the disclosure of which is incorporated herein by reference. Although resilient, the arms may be flimsy and require adjustment by tools. Therefore, it is desired that the clip on mechanism the resilient, easy to use and not require adjustment.